1. Field of the Invention
The present invention relates to an amine compound, an electrophotographic photoreceptor using the amine compound and an image forming apparatus having the same.
2. Description of the Related Art
An image forming apparatus for forming images using electrophotographic technology (hereinafter referred to as an electrophotographic apparatus) has been used frequently such as for copying machines, printers or facsimile units. In the electrophotographic apparatus, images are formed by way of the following electrophotographic process. At first, a photosensitive layer of an electrophotographic photoreceptor equipped in the apparatus (hereinafter referred to as a photoreceptor) is uniformly charged to a predetermined potential by charging means such as a charging roller, applying exposure in accordance with image information by exposure means, thereby forming an electrostatic latent image on the photoreceptor. A developer is supplied to the formed electrostatic latent images and a toner as a component of the developer is adhered to the surface of the photoreceptor to develop the electrostatic latent image and visualize it as toner images. Thus formed toner image is transferred by transfer means from the surface of the photoreceptor onto a transfer material such as recording paper and fixed onto the transfer material by fixing means. Further, cleaning is applied to the photoreceptor after transfer of the toner image by cleaning means having a cleaning blade, etc. thereby eliminating the toner and the like remaining on the surface of the photoreceptor not transferred to the transfer material during transfer operation. Then, the surface of the photosensitive layer is charge-eliminated by a charge eliminator or the like to erase the electrostatic latent image.
In recent years, the electrophotography has been utilized not restricted only to the field of the image forming apparatus such as copying machines but utilized also in the field, for example, of printing plate materials, slide films or microfilms for which photography has been used so far, and it is also applied to high speed printers using lasers, Light Emitting Diode (abbreviated as LED) or Cathode Ray Tube (abbreviated as CRT) as a light source. Along with extension of the application range of the electrophotography, the demand for the electrophotographic photoreceptor has become higher and more versatile.
An electrophotographic photoreceptor is constituted by laminating a photosensitive layer containing a photoconductive material on a conductive support formed of a conductive material. As the electrophotographic photoreceptor, an inorganic photoreceptor having a photosensitive layer mainly containing an inorganic photoconductive material such as selenium, zinc oxide or cadmium has been used generally. While the inorganic photoreceptor has basic properties as the photoreceptor to some extent, it involves a problem such that the formation of the film for the photosensitive layer is difficult and plasticity is poor, and the production cost is expensive. Further, since the inorganic photoconductive material generally has high toxicity and suffers from great restriction in view of production and handling.
As described above, since the inorganic photoconductive material and the inorganic photoreceptor using the same involve many drawbacks, research and development have been progressed for organic photoconductive materials. Further, the organic photoconductive material has been studied and developed generally in recent years and it has been utilized not only for electrostatic recording devices such as the electrophotographic photoreceptor but also has been applied, for example, to sensor materials or organic Electro Luminescent (abbreviated as EL) devices.
The organic photoreceptor using the organic photoconductive material has advantages such that the film formation property for the photosensitive layer is favorable and the flexibility is excellent, as well as it is light in the weight, excellent in the transparency, and a photoreceptor showing good sensitivity to a wavelength region over a wide range can be designedeasilybyanappropriate sensitizingmethod. Thus, the organic photoreceptor has been under development as a predominant candidate for the electrophotographic photoreceptor.
While the organic photoreceptor has drawbacks in view of the sensitivity and the durability in the early stage, such drawbacks have been improved remarkably by the development of a function separated electrophotographic photoreceptor in which charge-generating function and charge-transporting function are separately attained by different substances. Further, the function separated photoreceptor also has an advantage, in addition to the advantage of the organic photosensitive material described above, that the selection range for the material constituting the photosensitive layer is wide and an electrophotographic photoreceptor having optional characteristics can be manufactured relatively easily. The function separated photoreceptors include a lamination type and a single layer type. The lamination type function separated photoreceptor is provided with a lamination type photosensitive layer in which a charge-generating layer containing a charge-generating substance for charge-generating function and a charge-transporting layer containing a charge-transporting substance for charge-transporting function are laminated. The charge-generating layer and the charge-transporting layer are formed usually in a state where the charge-generating substance and the charge-transporting substance are dispersed respectively in a binder resin as a binder. Further, the single layer type function separated photoreceptor is provided with a photosensitive layer of a single layer type in which both of the charge-generating substance and the charge-transporting substance are dispersed in a binder resin.
As the charge-generating substance used in the function separated photoreceptor, various substances such as phthalocyanine pigment, squilirium dye, azo pigment, perylene pigment, polycyclic quinone pigment, cyanine dye, squalic acid dye and pyrylium salt dye have been studied and various materials of high light fastness and high charge-generating ability have been proposed.
Further, various compounds have been proposed as the charge-transporting material, for example, pyrazoline compounds (for example, refer to Japanese Examined Patent publication JP-B2 52-4188 (1977)), hydrazone compounds (for example, refer to Japanese Unexamined Patent Publication JP-A 54-150128 (1979), Japanese Examined Patent Publication JP-B2 55-42380 (1980), Japanese Unexamined Patent Publication JP-A 55-52063 (1980)), triphenylamine compounds (for example, refer to Japanese Examined Patent Publication JP-B2 58-32372 (1983), and Japanese Unexamined Patent Publications JP-A 2-190862 (1990) and stilbene compounds (for example, Japanese Unexamined Patent Publications JP-A 54-151955 (1979) and JP-A 58-198043 (1983)).
The charge-transporting substances must satisfy the following requirements:    (1) they are stable to light and heat,    (2) they are stable to active substances such as ozone, nitrogen oxide (chemical formula: NOx) and nitric acid generated by corona discharging in charging the photoreceptor,    (3) they have high charge-transporting ability,    (4) they have high compatibility with an organic solvent and a binder resin, and    (5) they can be manufactured easily and inexpensively. However, while the charge-transporting substances disclosed in, for example, the above-stated JP-B252-4188, JP-A54-150128, JP-B2 55-42380, JP-A 55-52063, JP-B2 58-32372, JP-A 2-190862, and JP-A 54-151955, JP-A 58-198043, can satisfy a portion of the demands but have not yet satisfy all of the demands at high level.
Further, in recent years, of the above-stated demands, particularly high charge-transporting ability has been demanded for the charge-transporting substance. For example, higher sensitivity has been demanded as the photoreceptor characteristics corresponding to the requirement of reduction in the size and high speed operation to electrophotographic apparatuses such as copying machines and printers, and the charge-transporting ability of the charge-transporting substance has been demanded to improve as means for attaining higher sensitivity of the photoreceptor. Further, in the high speed electrophotographic process, since the time from exposure to the development is short, a photoreceptor of excellent light responsiveness has been required. In a case where the light responsiveness of the photoreceptor is poor, that is, the decaying speed of the surface potential of the photosensitive layer by exposure is slow, the residual potential rises and is used repetitively in a state where the surface potential is not decayed sufficiently. Therefore, the surface charges at a potion to be erased are not sufficiently erased by exposure to cause deterioration of the picture quality such as lowering of the image density in an early stage. In the function separated type photoreceptor, the charges generated from the charge-generating substance upon light absorption are transported by the charge-transporting substance to the surface of the photosensitive layer so that the surface charges of the photosensitive layer at a portion irradiated with a light are eliminated. Therefore, the light responsiveness depends on the charge-transporting ability of the charge-transporting substance. Accordingly, high charge-transporting ability is required for the charge-transporting substance also with a view point of attaining a photoreceptor having high light responsiveness and capable of forming high quality images also in a high speed electrophotographic process.
Further, high durability of the electrophotographic apparatus is also required. In order to attain the high durability, it is necessary that the electrophotographic photoreceptor has excellent durability to electric and mechanical external force and can operate stably for a long period of time. For example, as to the mechanical durability, durability of the surface layer of the photoreceptor is important. In a case where a photoreceptor is used being mounted on an electrophotographic apparatus, the surface layer of the photoreceptor is inevitably scraped at a portion thereof by a contact member such as a cleaning blade or a charge roller. In a case where the amount of film reduction on the surface layer of the photoreceptor is large, since the charge retainability of the photoreceptor is lowered failing to provide high quality images. Accordingly, in order to attain higher durability of the electrophotographic apparatus, it is demanded for a photoreceptor having a surface layer of high mechanical durability resistant to the contact member, that is, having a surface layer of high printing resistance with less amount of film reduction.
In the above-described photoreceptor having the charge-transporting layer as the surface layer, in order to increase the printing resistance of the surface layer and improve the mechanical durability of the photoreceptor, it is presumable to increase the content of the binder resin in the charge-transporting layer used as the surface layer. However, in a case where the content of the binder resin is increased, since the content of the charge-transporting substance in the charge-transporting layer is relatively decreased, this brings about a problem that the charge-transporting ability of the charge-transporting layer is deteriorated and the light responsiveness is lowered. Since the light responsiveness of the photoreceptor depends on the charge-transporting ability of the charge-transporting substance as described above, a particularly high charge-transporting ability is demanded for the charge-transporting substance also for increasing the content of the binder resin thereby improving the mechanical durability of the photoreceptor, without lowering the light responsiveness.
However, the charge-transporting ability of the charge-transporting substances disclosed in, for example, JP-B2 52-4188, JP-A 54-150128, JP-B2 55-42380, JP-A 55-52063, JP-B2 58-32372, JP-A 2-190862, JP-A 54-151955, and JP-A 58-198043, is not sufficient. Even with these charge-transporting substances, it is impossible to obtain a photoreceptor having sufficient sensitivity and light responsiveness for attaining reduction in the size, high speed operation, and high durability of the electrophotographic apparatus.
Further, it is demanded for the electrophotographic apparatus that uniform images can be provided irrespective of the working circumstance and it is also required for the photoreceptor that the characteristics less change by fluctuation of circumstances such as temperature and humidity and it is excellent in circumstantial stability. However, photoreceptors using charge-transporting substance as disclosed, for example, in the above-stated JP-B2 52-4188, JP-A 54-150128, JP-B2 55-42380, JP-A 55-52063, JP-B2 58-32372, JP-A 2-190862, JP-A54-151955, and JP-A58-198043, have no sufficient circumstantial stability. Particularly, the sensitivity and the light responsiveness under a low temperature circumstance are not sufficient and, when the electrophotographic apparatus having such photoreceptors are used under the low temperature circumstance, they result in a problem of causing degradation of picture quality such as lowering of image density.